Tiantai or T'ien-t'ai is an East Asian Buddhist school of Mahāyāna Buddhism that developed in 6th-century China. Tiantai Buddhism emphasizes the "One Vehicle" (Ekayāna) doctrine derived from the Lotus Sūtra as well as Mādhyamaka philosophy, particularly as articulated in the works of the 4th patriarch Zhiyi. Brook Ziporyn, professor of ancient and medieval Chinese religion and philosophy, states that Tiantai Buddhism is "the earliest attempt at a thoroughgoing Sinitic reworking of the Indian Buddhist tradition." According to Paul Swanson, scholar of Buddhist studies, Tiantai Buddhism grew to become "one of the most influential Buddhist traditions in China and Japan."

East Asian Buddhism or East Asian Mahayana is a collective term for the schools of Mahāyāna Buddhism that developed across East Asia which follow the Chinese Buddhist canon. These include the various forms of Chinese, Japanese, Korean, and Vietnamese Buddhism in East Asia. East Asian Buddhists constitute the numerically largest body of Buddhist traditions in the world, numbering over half of the world's Buddhists.